The present disclosure relates to a device including, and a method for producing, an electric insulator which is made of plastic and has a centrally arranged core or hollow core. The insulator may be made of a glass-fiber-reinforced plastic material and may have a plurality of insulation screens which are arranged coaxially around the core in an offset manner in the axial direction of the core.
A method as well as a pertaining device for producing a plastic insulator are known from German Patent Document DE-AS 2044179 and a counterpart British Patent No. 1,316,059. There, a casting mold, which is open at the top, is arranged coaxially around a centrally arranged and vertically positioned core. This casting mold is then filled by pouring in a liquid silicone mass. In this case, with respect to its cavity, the mold has a contour which corresponds to the desired insulation screen. After the hardening of the silicone mass, the casting mold is moved axially downward, specifically by the amount which corresponds to the desired axial spacing of two insulation screens. The individual insulation screens are cast in this manner.
A problem of the known method is that the silicone mass, from which the insulation screens are cast, should have a relatively low viscosity, particularly equal to or lower than 25,000 mPa*s. In order to obtain a surface of the insulation screens which is favorable with respect to the insulation, filling materials can be added to the silicone mass only to a very limited degree. This increases the costs of the material of the insulator considerably.